It is already known from Swedish Patent Application 8801831-2 to determine the roll angle position with the aid of polarized electromagnetic radiation, comprising a transmitter arranged to emit a polarized radiation in the direction towards the projectile and a polarization sensitive receiver arranged in the projectile. By having the emitted polarized radiation consist of at least two mutually phase-locked radiation components with a wave-length ratio of 2:1 and/or multiples thereof, which are superposed and form an asymmetrical curve shape, the roll position of the projectile can be unambiguously determined.
This prior art requires that a transmitter is placed in connection with the launching position of the projectile and that the projectile is provided with a rearward-directed receiving antenna in order to receive the transmitted radiation.
Furthermore it is necessary that two mutually phase-locked radiation components with different frequencies are transmitted. This means that both the transmitter and the receiver are of a relatively complicated construction.
It is also already known from EP 0,341,772 to determine the roll angle position by giving the one carrier wave a sinusoidal amplitude modulation in order to continuously transmit information on the phase position. As described in this patent such a system has is advantageous due to simpler construction of the receiving part in the projectile. However, two antennae of known relative orientation are required in the receiver.